1. Field of the Invention
The invention pertains to a vehicle seat belt controller for controlling the tension of a three-point seat belt installed in a vehicle, e.g., a driver's seat of the vehicle.
2. Description of Related Art
Seat belt units and airbag units are conventionally installed in a vehicle, such as an automobile, for the purpose of restraining the occupants in the event of a collision. Of these two units, the seat belt unit is also used to restrain the occupants during normal travel, i.e., other than during a collision. Thus, it is desirable to create a proper sense of restraint for the occupants according to the given travel conditions of the vehicle.
Related vehicle seat belts adopt a so-called three-point seat belt unit with a structure to restrain seated occupants at three points, that is, at the lumbar region and at either the right or the left shoulder. More specifically, a right shoulder-restraining seat belt includes a structure that restrains the lumbar region and the right shoulder, and is generally used for those seats provided on the right-hand side of the vehicle. Conversely, a left shoulder-restraining seat belt includes a structure that restrains the lumbar region and the left shoulder, and is generally used for those seats provided on the left-hand side of the vehicle.
When related right and left shoulder-restraining seat belts are both controlled in unison in response to a lateral load that acts on the occupants, e.g., when the vehicle makes a turn, there is the risk that the conventional shoulder-restraining seat belt may inappropriately fit the occupant. That is, if both the right and left shoulder-restraining seat belts are controlled uniformly, e.g., the same seat belt timing take-up is used, then an occupant might experience discomfort due to the related shoulder-restraining seat belt.
For example, as a vehicle makes a right turn, a leftward centrifugal force acts on the occupants, and the bodies of the occupants tend to move toward the left. For those occupants seated in seats equipped with conventional right shoulder-restraining seat belts, an appropriate restraining effect may be achieved. However, for those occupants seated in the seats equipped with left shoulder-restraining seat belts, the same seat belt take-up operation as applied to the right shoulder-restraining seat belts is potentially undesirable in that the left shoulder-restraining seat belts may shift from the left shoulder to the neck of an occupant, thereby potentially causing the occupant to experience discomfort.